Grinding machines

ABSTRACT

A grinding machine for thread or similar form grinding or cylindrical grinding is disclosed in which radial infeed of the grinding wheel head to a workpiece carried by a work support arranged for relative traversing movement, is incrementally effected by a stepping motor drive on the wheel head to a lead screw via a gear drive having a driving and slidable engagement with the lead screw which latter cooperates with a fixed nut on the machine base, fluid pressure operated piston and cylinder means being provided and acting between the wheel head and lead screw for relative rapid initial feed and retraction movements of the wheel head as permitted by the sliding engagement of the stepping motor gear drive with the lead screw.

United States Patent [72] Inventor Raymond L. Palmer Solihull, England [21] AppLNo. 836,099 [22] Filed June 24,1969 [73] Assignee Coventry Gauge & Tool Company, Limited Coventry, Warwickshire, England [54] GRINDING MACHINES 5 Claims, 3 Drawing Figs.

[52] U.S.Cl 51/95, 51/165.8,51/165.82,51/165.9,51/165.87 [51] Int.C1. B24b3/00, B24b49/00 [50] FieldoiSearch ..51/95,95.1, 165.8, 165.71, 165.87,165.9, 165.82

[56] References Cited UNITED STATES PATENTS 1,993,830 3/1935 Conover 51/165.14 2,333,341 11/1943 Scrivener 51/165.07 2,337,223 12/1943 Armitage 5l/165.07 2,489,666 11/1949 0verstedt..... 51/165.08 2,648,171 8/1953 Hill 51/95.1

Primary Examiner-William R. Armstrong Att0rneyWatson, Cole, Grindle & Watson ABSTRACT: A grinding machine for thread or similar form grinding or cylindrical grinding is disclosed in which radial infeed of the grinding wheel head to a workpiece carried by a work support arranged for relative traversing movement, is incrementally effected by a stepping motor drive on the wheel head to a lead screw via a gear drive having a driving and slidable engagement with the lead screw which latter cooperates with a fixed nut on the machine base, fluid pressure operated piston and cylinder means being provided and acting between the wheel head and lead screw for relative rapid initial feed and retraction movements of the wheel head as permitted by the sliding engagement of the stepping motor gear drive with the lead screw.

PATENTED JAN 4 I972 SHEET 1 0F 2 INVENTOR RAYMoNu Lzsu: PALMEQ ATTORNEY 4L4 /ZM%, WW

PATENTEBJAN 41912 3,831,633

SHEET 2 [IF 2 IO 7 b 57 56 4o 0 5 I Q -/Z i a E. I4 [2 I40 I30 lb [7 l8 FIG. 2.

ENTOR YM N LESLIE PALMER ATToczNr GRINDING MACHINES This invention relates to grinding machines for carrying out thread or similar form grinding or cylindrical grinding on workpieces and has for its primary object to provide improved means therein for effecting grinding wheel head infeed and retraction in relation to a workpiece carried by the machine work support.

A further object of the invention to provide an improved grinding machine incorporating such wheel head infeed and retraction means operating in conjunction with other mechanism of the grinding machine such as work support traversing means and wheel dressing means. Practical advantages of the invention will be apparent from the following disclosure.

By the term stepping motor" as used herein, is meant a pulse-operated synchronous induction electric motor of which the output rotary member or shaft thereof is driven for angular movement in precise steps or increments according to the pulse operation of the motor by programming apparatus which is controlled by punches or magnetic tape or otherwise operated.

In a practical embodiment of the invention as applied to a screw thread or form-grinding machine, the construction and arrangement of the machine is as follows, reference being had to the accompanying diagrammatic drawings in which:

FIG. 1 is a front elevation of the general mechanism of the machine,

FIG. 2 is an end view in the direction of the arrow II of FIG. 1 and,

FIG. 3 is a detail diagram of the grinding wheel motor drive.

As hereafter described the work support or table 3 is arranged to be traversed axially on the machine base 2 relative to the wheel head 1 carrying the grinding wheel 10 while the wheel head 1 is slidably mounted on the base 2 for horizontal feeding or retracting radial movement (i.e., forward and backward) in relation to a workpiece supported on the machine table 3 and arranged to be driven from the work head 4 on the latter.

For such feeding and retracting movement the wheel head 1 is actuated by lead screw mechanism 12 preferably of the recirculating ball type and in accordance with one aspect of this invention the lead screw mechanism 12 is driven by a stepping motor 11 through worm and worm wheel gear 13.

Operation of the screw 14 of the mechanism 12 and hence positioning of the wheel head I is controlled by a programmed sequence of pulse inputs to the motor 11 to effect movement of the wheel in a predetermined configuration or cyclic pattern e.g., for carrying out plunge grinding, single one-way grinding, double one-way grinding, multiple one-way grinding and two-way grinding in a particular manner involving feed or feedbackless passes or any combination of variations of such motions.

Whereas the stepping motor drive 11 can be advantageously effected as herein described for the purpose of a grinding operation and for wheel dressing compensation, there is also provided hydraulic or other means for effecting relatively rapid retraction of the wheel head 1 e.g., for moving the wheel 10 clear of the workpiece 5 after a grinding operation and also for rapid advance or infeed closely up to the grinding position.

Thus referring to FIG. 2, the wheel head 1, which is slidably mounted on the base 2 such as by hydrostatic slideways for movement towards and away from the workpiece 5, has a part 16 depending into the base 2 which carries the stepping motor 11 and worm and worm wheel drive 13 of which the worm wheel 13a slidably engages a splined portion 14a of the lead screw 14 which latter has a screw engagement with a nut 15 fixed in the base 2. The other end of the lead screw 14 carries a piston 17 of a fluid pressure operated or hydraulic doubleacting piston and cylinder arrangement, the cylinder 18 of which is carried by the depending part 16 for effecting rapid movement of the work head 1 on the base 2 relative to the lead screw 14 for initial infeed or retraction of the grinding wheel 10 in relation to the workpiece 5. Retraction of the wheel head 1 in this way is preferably to a datum position in relation to which incremental feed and/or wheel dressing compensation is effected by the stepping motor drive II to the lead screw 14.

In the arrangement of supporting and driving the workpiece 5, the machine worktable 3 is arrangedfor lead screw operation at 30 while the faceplate 40 or other work driving means of the work head 4 on the table 2 is driven in timed relationship with the table lead screw 30 through a suitable gear drive. Thus referring to FIG. 1 and from a motor drive (not shown) in the machine base 2 a splined shaft 20 is driven which is slidably engaged by an initial gear of a gear train 42 which extends from the work head 4 into the machine base 2. Through gearing 43 affording a highor low-ratio drive, the gear train drives the faceplate spindle 41 of the work head 4.

Through change gears 44, the gear train 42 drives a further gear train 45 which in turn drives the lead screw 30 carried by the worktable or slide 3 which is slidable on the base 2 i.e., the lead screw 30 moves axially with the worktable 3 as it imparts movement to the latter through the thrust bearing 37 on rotation relative to the cooperating nut 22 carried by the base.

The lead screw 30 and nut 22 are preferably of the recirculating ball type while the nut 22 is constrained against axial movement relative to the base 2 but is rotatable therein for the purpose referred to below.

For thread or similar grinding the workpiece 5 is supported and driven in the above manner, but for compensating or other movement during such grinding or for various other kinds of grinding operations, the worktable 3 is arranged to be driven in an independent manner by a stepping motor 31 arranged for programmed operation i.e., in conjunction with that of the stepping motor drive 11 to the wheel head 1.

For this purpose the stepping motor 31 to the worktable 3 is arranged to drive the nut 22 for angular movement so that as the nut 22 is turned in this way the lead screw 30 is axially advanced or retarded for effecting corresponding movement of the table 3. Thus by appropriately sequenced pulse input to the stepping motor 31 incremental traverse of the worktable 3 is obtained for effecting backlash or other compensation and ensuring proper or appropriate engagement of the grinding wheel 10 with the workpiece 5.

In the arrangement shown the stepping motor 31 drives the nut 22 through a worm and worm wheel drive 33, differential gear 32 and gear train 34.

As well as relative positioning of the wheel 10 and workpiece 5 e.g., for multistart thread grinding, the stepping motor drive 31 may be also employed for traversing the table in carrying out annular grinding especially where a series of annular grooves or other ground formations are required on the workpiece 5. For this or other grinding purposes the stepping motor traverse of the table 3 may be such as to obtain spacing apart of ground portions of the workpiece 5.

In a development of this aspect of the invention, the worktable stepping motor drive 31 is shown operating in conjunction with a further electric motor drive 35 of the table 3 i.e., to the nut 22 for obtaining rapid traverse e.g., in returning the workpiece 5 for a further pass relative to the grinding wheel 10 or for effecting greater spacing apart between ground portions of the workpiece 5 than is feasible by the stepping motor drive 31. The further electric motor 35 for this purpose may consist of an AC three-phase squirrel cage induction motor and, in conjunction with the stepping motor 31, is arranged to be selectively caused to drive the nut 22 i.e., through worm and worm wheel drive 36, the differential gear 32 and the gear train 34. As will be appreciated the differential gear 32 provides a constant-mesh arrangement for permitting either the stepping motor 31 and/or the rapid traverse motor 35 to drive the nut 22 as required.

Particularly by operation of the rapid traverse motor 35, traverse of the worktable 3 can be effected independently of the drive to the work head spindle 41 so that driving of the latter and associated gear trains can be kept to a minimum.

Further in accordance with this invention the wheel head stepping motor drive 11 and also the worktable stepping motor drive 31 operate in conjunction with stepping motor operated grinding wheel dressing means 50 mounted in position of use on the grinding wheel head 1.

Thus dressing tool holder means 52 of the dressing apparatus for holding one or more dressing tools 52a according to the nature of the work profile is slidably mounted on the wheel head 1 for feeding and retracting movement in relation to the periphery of the grinding wheel 10.

The dressing toolholder is shown operated for such movement by screw mechanism 53 which is preferably of the recirculating ball type of which the screw 54 is driven by the associated stepping motor 51 through worm and worm wheel gear 55.

Programmed operation of the stepping motor 51 is arranged to effect feed of the dressing tool 52a to the wheel and retraction therefrom in accordance with the nature of the grinding operation e.g., at suitable intervals during the latter. Whereas it is preferable to effect purely automatic dressing of the grinding wheel 10 in this way, if desired, dressing may be effected at will or manually by appropriate operation of the programming apparatus.

The sequence of operation of the dresser 50 may be such that a diamond tool 52a or tools thereof performs a predetermined number passes in relation to the wheel 10 with a required amount of diamond tool feed applied at each or either end of the path of diamond tool movement or at any other desired point by the stepping motor drive 51.

The stepping motor drive 51 to the dresser may operate in conjunction with means such as an electrically controlled hydraulic actuator for effecting linear and/or arcuate or other movements of the diamond tool 52a or each thereof for performing wheel dressing in accordance with the peripheral profile of the wheel 10. The hydraulic actuator may be operated by solenoid-operated valve means in a double-acting manner.

Operation of the stepping motor drive 51 to the dresser 50 in conjunction with the stepping motor drive 11 of the wheel head 1 readily enables compensating increments of feed to both the diamond tool 520 or tools and the wheel head 1 to be carried out in an appropriate and corresponding manner, the increments of feed being equivalent to the amount of wheel wear occasioned by dressing and/or grinding.

Provision such as hydraulic operation may be included for relatively rapid advance and retraction of the dressing toolholder 52 in relation to the grinding wheel 10 with final incremental feed and retraction effected by the stepping motor drive 51.

Where the dresser 50 includes two or more dressing tools at 520, a stepping motor drive 51 or other operation thereof may be such as to bring first one dressing tool or tools in dressing contact with the wheel 10 and then the other dressing tool or tools in contact therewith in order to complete the dressing of the various parts of the wheel profile such as the flanks and crest of a V-forrn profile.

By means of the encoders 19,39 to the stepping motors 11,31 controlled operation of the latter in relation to one another can be effected in conjunction with their pulse operation by programming apparatus e.g., of the punched tape operated type. Thus particularly in the case of the stepping motor traverse of the worktable 3, the resulting linear movement of the latter may be monitored by the encoder 39 to the motor 31 which provides a feedback reference to a controlling device for comparison with the program as predetermined for a particular grinding operation.

For grinding purposes the grinding wheel 10 is driven from a main motor 6 by a belt drive 7 but during dressing the wheel 10 is driven by a lower powered motor 56 via a belt drive 57, a suitable clutch 58 on the shaft 611 of the main motor 6 and belt drive 7.

The grinding wheel 10 may be set to the required angle of inclination relative to the workpiece 5 (e.g., in accordance with thread form helix angle of the latter) by corresponding angular setting of the wheel head 1 which is shown effected by gear mechanism 9.

lclarm:

l. A grinding machine of the character described comprising a base structure; a work support mounted for horizontal traversing movement on said base structure; a work head carried by said work support; work driving means carried by said work head for driving a workpiece supported by said work support; lead screw and nut mechanism in gear-driven relationship with the work driving means and operating between the base structure and work support for imparting at least operative traversing movement to the latter on operation of the work driving means: a wheel head slidably mounted on the base structure for radial infeed and retraction movement relative to a workpiece carried by the work support; a grinding wheel rotatably carried by said wheel head; motor drive means carried by the wheel head for driving said grinding wheel; a nut fixed on the base structure; a wheel head feed lead screw engaging said nut; a gear drive having a driving and slidable engagement with the lead screw; a wheel head feed stepping motor carried by the wheel head for programmed operation in driving the lead screw via said gear drive and thus effecting incremental infeed of the wheel head and grinding wheel carried thereby in relation to work support traverse; and fluid pressure operated cylinder and piston means acting between the wheel head and lead screw for rapid infeed and retraction movements of the wheel head relative to the lead screw as permitted by the sliding engagement of the said gear drive with the latter.

2. A grinding machine according to claim 1 wherein the gear drive between the stepping motor and wheel head feed lead screw consists of a worm and worm wheel drive of which the worm wheel has a driving and sliding engagement with the lead screw by engagement with a splined portion thereof.

3. A grinding machine according to claim 1 wherein the lead screw of the lead screw and nut mechanism acting between the base structure and work support for traversing the latter, is carried by the work support and the cooperating nut is rotatably mounted on the base structure but constrained against axial movement relative thereto; there being provided in combination therewith a gear drive to said rotatable nut and a traverse stepping motor on said base structure for programmed operation in imparting rotation to said nut via the gear drive for effecting independent incremental traverse movement of the work support.

4. A grinding machine according to claim 3 wherein the gear drive to the rotatable nut consists of a differential gear through which the traverse stepping motor drives said nut and an electric motor also in driving connection with the nut via said differential gear for effecting rapid traverse movement of the work support especially return traverse.

5. A grinding machine according to claim 1 wherein grinding wheel dressing means is slidably carried by the wheel head for feeding and retracting movement in relation to the periphery of the grinding wheel; screw mechanism being provided for imparting said movement to the dressing means, said screw mechanism being gear driven for incremental feed movement to compensate for grinding wheel wear by a stepping motor for programmed operation in conjunction with the wheel head feed stepping motor. 

1. A grinding machine of the character described comprising a base structure; a work support mounted for horizontal traversing movement on said base structure; a work head carried by said work support; work driving means carried by said work head for driving a workpiece supported by said work support; lead screw and nut mechanism in gear-driven relationship with the work driving means and operating between the base structure and work support for imparting at least operative traversing movement to the latter on operation of the work driving means: a wheel head slidably mounted on the base structure for radial infeed and retraction movement relative to a workpiece carried by the work support; a grinding wheel rotatably carried by said wheel head; motor drive means carried by the wheel head for driving said grinding wheel; a nut fixed on the base structure; a wheel head feed lead screw engaging said nut; a gear drive having a driving and slidable engagement with the lead screw; a wheel head feed stepping motor carried by the wheel head for programmed operation in driving the lead screw via said gear drive and thus effecting incremental infeed of the wheel head and grinding wheel carried thereby in relation to work support traverse; and fluid pressure operated cylinder and piston means acting between the wheel head and lead screw for rapid infeed and retraction movements of the wheel head relative to the lead screw as permitted by the sliding engagement of the said gear drive with the latter.
 2. A grinding machine according to claim 1 wherein the gear drive between the stepping motor and wheel head feed lead screw consists of a worm and worm wheel drive of which the worm wheel has a driving and sliding engagement with the lead screw by engagement with a splined portion thereof.
 3. A grinding machine according to claim 1 wherein the lead screw of the lead screw and nut mechanism acting between the base structure And work support for traversing the latter, is carried by the work support and the cooperating nut is rotatably mounted on the base structure but constrained against axial movement relative thereto; there being provided in combination therewith a gear drive to said rotatable nut and a traverse stepping motor on said base structure for programmed operation in imparting rotation to said nut via the gear drive for effecting independent incremental traverse movement of the work support.
 4. A grinding machine according to claim 3 wherein the gear drive to the rotatable nut consists of a differential gear through which the traverse stepping motor drives said nut and an electric motor also in driving connection with the nut via said differential gear for effecting rapid traverse movement of the work support especially return traverse.
 5. A grinding machine according to claim 1 wherein grinding wheel dressing means is slidably carried by the wheel head for feeding and retracting movement in relation to the periphery of the grinding wheel; screw mechanism being provided for imparting said movement to the dressing means, said screw mechanism being gear driven for incremental feed movement to compensate for grinding wheel wear by a stepping motor for programmed operation in conjunction with the wheel head feed stepping motor. 